1. Field of the Invention
The present invention relates to a lens-fitted photographic film unit, and more particularly to a telephoto-type lens-fitted photographic film unit having a Z-shaped and elongated optical path and a lens aperture changing mechanism.
2. Related Art
Various types of lens-fitted photographic film units, hereinafter referred to as film units, have been widely known, each of which is pre-loaded with film and has a simple picture-taking mechanism so that anyone can easily enjoy photography.
U.S. Pat. No. 5,084,719 discloses a telephoto-type film unit whose taking lens has a focal length of about 70 to 80 mm and an f-number of f/12 to 14. The lens is disposed in substantially the same plane as the front wall of the unit housing. A pair of mirrors are arranged to define a Z-shaped light path inside the unit housing, so that the light path may be long enough for telephotography, without the need for increasing the thickness of the housing.
The unit housing of the known telephoto-type film unit is basically constituted of a main body and front and rear covers removably attached to the main body. The main body is formed from a synthetic resin as an integral body having a cassette chamber or film take-up chamber, a film roll chamber or film supply chamber, an exposure frame formed between these chambers and an exposure chamber disposed in front of the exposure frame to permit light from the taking lens to fall on the photographic film.
In the main body, a shutter base plate is attached to an upper front portion of the exposure chamber, and a barrel having a stray light shielding plate is inserted from above, behind the shutter base plate. The first mirror is attached to an upper oblique opening in the exposure chamber formed behind the barrel. A cover member having a mirror hold down portion is mounted to close the top opening of the exposure chamber and the first mirror. A shutter cocking mechanism and a film advancing mechanism are mounted to one side of the exposure chamber. A shutter blade is attached to the shutter base plate, and the second mirror is attached to a lower oblique opening formed in a lower front portion of the exposure chamber. A shutter cover having a mirror holding portion covers the front of the shutter blade and the second mirror. The shutter cover is secured to the exposure chamber through snap-in engagement without using screws or adhesives. Thereafter, the taking lens is assembled in a lens holder which is integrally formed with the shutter cover. After the front cover is attached to the main body, a film cassette and a roll of photographic film pulled out from the film cassette and wound in the roll are positioned in the cassette chamber and the film roll chamber, respectively, in a dark room, and the rear cover is attached to the rear of the main body.
Recently, in the interest of environmental protection or reduction of industrial waste, the unit housing of the used film unit is reused or recycled. The front and rear covers are melted to be recycled as a plastic material, because they are often damaged during the use or the disassembly of the film unit. The main body is also recycled as scrap plastic material, because the film roll chamber and the exposure frame directly contact the photographic film, and thus might damage the photographic film if any dust or particles are on these portions.
However, as the mirrors mounted on the main body are made from different materials, such as glass, than that of the main body, it is necessary for recycling the main body to remove the mirrors therefrom. Besides, the mirrors themselves can be reusable since they are protected from the ambient. Also the picture-taking mechanisms are reusable in most cases. Therefore, it is desirable to remove these reusable parts from the main body, so as to reuse them. It is known in the art of these film units to assemble the picture-taking mechanisms into a unit and removably attach this unit to the main body. But the mirrors can be easy to break and difficult to remove from the main body reliably. Therefore, the cost of recycling components of the telephoto-type film units has been great.
On the other hand, a telephoto-type single-use camera "KODAK FUN SAVER TELEPHOTO 35" (trademark) has been marketed by Eastman Kodak Company. This camera is loaded with a film of film speed of ISO 1600, and has a lens aperture changing mechanism for switching the lens aperture between a daylight photography mode, that is a mode suitable for picture-taking in sunny daylight, and a night game photography mode, that is a mode suitable for picture-taking of sporting events played at night under brightly flood-lit conditions. But the night game photography mode is suitable for picture-taking in cloudy daylight as well. To set the night game photography mode, a switching lever disposed on one side of the taking lens is operated to change the size of the lens aperture from f/11 to f/22. At the same time, a warning flag formed on the tip of the switching lever is placed in front of the viewfinder to indicate that the lens aperture size has been changed to the night game photography mode.
However, because the viewfinder of the Kodak camera is of the see-through type and has a filter with a high neutral density of about 1.8 log attached thereto, the warning flag is so inconspicuous that the photographer can overlook it and take a picture with an improper lens aperture size. Moreover, because a knob for operating the switching lever is disposed in the front of the camera housing, it is necessary to turn the camera toward the photographer every time mode switching or lens aperture changing is required.